Stool

ABSTRACT

The dental stool has a base with casters permitting movement into desired operating position. The seat is supported by a hinged arm mounting for the seat column lower end, permitting free movement of the column axis in all directions in a horizontal plane. The column length is adjustable for placing the seat at desired height and the seat has a tilting adjustment with respect to the column, and may turn freely about the column axis. The forward edge of the seat is recessed for supporting the thighs to either side of the recess and rearwardly thereof. A horizontal ring cooperating with a rotatable wheel on the column limits the movement with respect to the base and a horizontal plate cooperates with an adjustable spring pressed pad at the bottom of the column to provide a slight frictional resistance to movement of the stool seat and column.

[451 Apr. 10,1973

1 1 STOOL [76] Inventor: Richard W. Page, PO. Box 258 B,

Chatham, Mass. 02633 [22] Filed: Aug. 23, 1971 21 Appl. No.: 173,978

[52] US. Cl. ..297/349, 297/326, 248/416 [51] Int. Cl ..A47c 1/02 [58] Field of Search ..297/349, 326, 241, 297/240, 242; 248/415, 416, 418, 425, 282

[56] References Cited UNITED STATES PATENTS 1,484,229 2/1924 Miles ..297/349 X 1,678,668 7/1928 Collier 297/326 X 2,568,988 9/1951 Childs ..297/349 3,147,946 9/1964 Hale ....297/349 X 3,191,400 6/1965 Swenson ....297/349 X 2,424,729 7/1947 Andreasen... ....297/24l X 3,542,424 11/1970 Bingley 1 ..297/349 1,566,161 12/1925 Moore ..297/24l 2,848,037 8/1958 MacKnight 1 ..297/240 3,151,910 10/1964 Larson ..297/349 I r I r1 1i 1 1 r 11 r 2,678,086 5/1954 Mohr ..297/240 Primary Examiner-Francis K. Zugel Attorney-Sawyer E. Kennedy 1 [5 7] ABSTRACT The dental stool has a base with casters permitting movement into desired operating position. The seat is supported by a hinged arm mounting for the seat column lower end, permitting free movement of the column axis in all directions in a horizontal plane. The column length is adjustable for placing the seat at desired height and the seat has a tilting adjustment with respect to the column, and may turn freely about the column axis. The forward edge of the seat is recessed for supporting the thighs to either side of the recess and rearwardly thereof. A horizontal ring cooperating with a rotatable wheel on the column limits the movement with respect to the base and a horizontal plate cooperates with an adjustable spring pressed pad at the bottom of the column to provide a slight frictional resistance to movement of the stool seat and column.

6 Claims, 9 Drawing Figures PATENTED APRI 0 I973 sum 1 BF 5 INVENTOR.

PATENTEB APR] [H973 SHEET 3 BF 5 PATENTEDAPmmm SHEET b 0F 5 e4 e7 61 65 eoooobo fingililllilllllil d ,53 63 jjeo 58 [52 /@MJW STOOL BACKGROUND OF THE INVENTION Rotative and tilting free movement of stool seats have been provided, and permit a limited amount of shifting by the operator to relieve pressure on the legs which tends to disturb circulation and to flex the muscles and joints. It is also known to mount the stool support column for movement about a center adjacent the stool base so that the seat can move in a conical manner to relieve strain from sitting in a fixed position.

The present invention has as its general object to provide for a very much increased range of shifting about of an operator seated on the stool.

SUMMARY OF THE INVENTION The present invention provides a stool seat support which permits free movement of the seat in a horizontal plane, while confining such movement to a predetermined range and also providing a controlled and slight frictional resistance to movement. The seat support column combines with this support a seat height adjustment and pivotal movement about a vertical axis, while the seat is tiltable about a horizontal axis and centrally recessed at its forward edge so as to confine the pressure supporting the operators body to the strong musculature of the thighs and buttocks while avoiding pressure on the sensitive genital and perineal areas.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a side elevation of the stool;

FIG. 2 is a plan view of the lower part of the structure;

FIG. 3 is a front view corresponding to the plan view of FIG. 2;

FIGS. 4 and 5 are enlarged views of the jointed stool column support, respectively in horizontal section on line iv-iv of FIG. 5 and in extended side elevation;

FIGS. 6 to 8 are further enlarged and are, respectively, a bottom view, front elevation and profile thereof, showing the structure mounting the seat to the support column; and

FIG. 9 is a vertical section of the lower part of the stool seat support column.

The stool comprises a seat 1, with backrest 2, carried on a column indicated generally at 3, which is movably mounted on base 4 for shifting bodily in a horizontal plane.

Plate 5 on the base serves to stiffen the latter and provides a friction bearing surface. It does not support the column 3, but merely prevents uncontrolled sideslipping thereof. A ring 6 positioned above plate 5 and concentric with it serves to confine lateral movement of the post 3 within a central area of the plate 5.

The column 3 is supported and kept vertical, while permitting free horizontal movement, by an arm 7 hingedly joined to arm 8, which is pivotally carried in support 9.

The height of the seat is adjusted, as desired, between an uppermost limit (solid position; FIG. 1) and a lowermost limit (broken line position 1" of FIG. 1). The seat may be tilted (as to broken line position 1' of FIG. 1) about a horizontal axis adjacent post 3 and may also be rotated unrestrictedly and together with the justmentioned horizontal axis in a horizontal plane about the vertical axis of the post 3. As already mentioned, the seat may be moved horizontally, subject only to restriction of range of movement by the ring 6.

All of the foregoing movements are independent of the bodily placement of the stool as a whole, base and all, which placement movement, rotary or translational, is provided for by mounting the base on casters 19, as usual, or on glides, where preferred.

The seat 1 may have a variety of constructional features and configurations, depending upon the work in which it is used, and upon the preferences and physique of the operator. The seat shown is of a type adapted to dental work and is of a posture type, without arms and with an adjustable back rest or support member 2, which may be resiliently positioned. The seat proper comprises a rigid bottom plate structure to which the back support is attached and which is supported by the column or post 3 as later described, and which is surmounted by a padded or upholstered cushion, which may be of any desired construction, but is preferably comparatively thin and hard.

The middle of the front edge of the seat is recessed as at 1-r so as to avoid pressure upon the genital and perineal region between the legs and confine the support to the buttocks and upper thighs. As the operator makes the very numerous or frequent small movements, which are largely unconscious, the stool seat moves with him, so that sliding on the seat surface, with consequent bunching and wearing of the clothing, are minimized.

In the lowermost position of the seat (1" in FIG. 1) the upper surface of the seat may be about 18 inches from the floor, permitting the operator to sit with the thighs horizontal and the spine and lower part of the legs vertical. As is apparent from the geometry, the feet may be moved back or forward and the upper part of the body may lean forward without substantially affecting the buttock and thigh placement.

In the uppermost position of the seat l or 1' in FIG. 1) and with the operators feet on the floor, the thighs may be at an angle of about 20 to the horizontal. With conventional stools, such a position can be achieved only by moving forward on the seat into a position where the seat edge presses against the perineal region and/or genitals, and generally involves a bunching up of the clothing, which aggravates any resulting irritation. If a recess is incorporated in the front edge of the seat, this situation is pertly corrected, particularly if the seat has a forward tilt, but a full correction requires also free lateral shifting, which is provided by the stool of the invention.

Where a footrail is provided, the just mentioned conditions are altered, introducing, for any given height of the seat a different angulation of the thighs-when the feet are supported on the rail, with the heels hooked over it in some cases. This limits the shifting movements of the feet, and may require rearward tilting of the seat.

As will be apparent from the following description, the movements provided by the present invention include combined rotary and shifting movement of the post or column 3 corresponding to given tilt of the seat, such that the resultant motion reproduces that provided by a conical movement of a stool support post about a universal joint at its base.

The structural elements by which the above adjustments or movements are obtained, will now be described in detail.

The base structure 4, previously referred to, comprises a number (five, as shown) of horizontal arms 11-15 radiating from a central hub 16, to which they are welded or otherwise fixed. The plate overlies the structure 1l16 and may be welded or otherwise secured thereto so as to stiffen and strengthen the base structure. Plate 5 has a lateral extension 17 along radius arm 11, and supporting the assembly 9, as later described.

Caster mounts 18 at the ends of arms 11, etc., receive the shanks of casters 19, which may be of any available preferred type and may also be replaced by glides.

Diagonal struts or braces 20 connect arms 11 ,12 and 11,15, serving to stiffen the structure and to assist-in transferring the load from assembly 9 to arms 12 and 15, hub 16 and arms 13 and !4.

The supporting structure indicated generally by reference numerals 7-9 is shown in detail in FIGS. 1 to 5. The (shoulder) support 9 includes upper and lower plates 21,22 and vertical column 23, these elements being weldedtogether, or otherwise joined or formed so as to form a rigid structure. Lower plate 21 is secured to extension 17 of plate 5 and to subjacent elements 11,20. Aligned bores in the plates 21,22 receive vertical pin or shaft 24 on which the hub 25 of arm 8 (upper arm) is rotatably or hingedly supported. Upper and lower needle bearings 26 and 27 transmit any force couple about a horizontal axis from arm 8 to support frame 2143, but do not transmit any vertical force component. The vertical support for the hub 25 is provided by washer plate 28 and thrustbearing 29, which sits on plate 21. Set screw 30 holds pin 24 in. place in plate 22, and head 31 on the pin 24 supports the ring 6, previously referred to, and which may be welded to the head 31 v 1 Arm 8 has a hub 32 at its other (elbow) end, rotatively mounting vertical hinge pin 33 by means of upper and lower needle bearings 35 and 36, which transmit any force couple about a horizontal axis from arm 7 to arm 8. Pin 33 is carried in bores in the (forearm) arm 7 and secured therein by set screws 33'. The vertical load is transferred from arm 7 to hub 32 by thrust bearing and washer 34,34 and only rotary couples about horizontal axes are transmitted by needle bearings Arm 7 comprises a hub 37 with upper and lower plates 38,39 and incorporates a tubular section 40 above and below these plates, which accommodates and supports the components of the seat support post or column 3. The lower end of section 40 is threaded, as at 41, and carries an assembly 43-46 for positioning and holding a friction disk 42 in contact with plate 5, under predetermined and adjustable pressure, for providing a controlled (and slight) frictional opposition to horizontal displacement of the seat support column 3. Lock nut 43 and upper (outer) cup elementd44 screw onto threaded section 41 and lower (inner) cup member 45 is slidably received in member 44. Spring 46 pushes member 45 and the friction disk 42 carried thereon down against plate 5. The pressure is adjusted by by changing the height of lock nut 43 and cup member 44. The pressure exerted will ordinarily be only a few pounds and the frictional resistance to movement only about a pound or so.

The upper end of tubular section 40 carries a roller 49, which engages the ring 6, and is held in place vertically by collars 47,48 on the tubular section 40. The vertical axis of roller 49 and of seat support post 3 is thereby kept on or inside of the circle C (FIGS. 2 and 4), while offering no opposition to movement while within this area.

Arms 7 and 8, when in their most closed position, are at an angle of about 25 (1 PQS). In their most extended position, this angle opens up to about 125 (1 P"Q"S). If the movement of axis P is followed clockwise around the circle C (FIG. 2), starting with the most closed position, it will be noted that the arm 8 first swings counter clockwise, until the parts reach approximately the solid line position of the figure. Thereafter, arm 8 swings clockwise and the angle between arms 7 and 8 continues to open up until the fully extended position (SQ"P") is reached. As the axis P continues around circle C for another 45 or so, the angle starts closing, but arm 8 continues to swing clockwise. Thereafter (from a position of axis P over the base radius arm 13) the angle continues to close and arm 8 swings counterclockwise until the starting position (SQP') is reached. Anywhere within circle C, the axis P may move horizontally in any direction by rotating arm 7 about a stationary axis 0, by rotating arms 7 and 8 at fixed opening angle about the center S, or by a combined movement of the arms 7 and S'about the two centers or axes. There is one and only one position of the arms 7 and 8 corresponding to any position of axis P, and in no case is there any dead center effect.

The very slight opposition to movement which is interposed by friction pad 42 serves to prevent skidding or overshooting movements of the stool seat. It also holds against any slight tendency to movement which might be created by slant of plate 5 due to an out of level floor, or due to such slight horizontal force component as may be transmitted by seat support post 3-A due to horizontal pressure of the operators feet whlie the operator is sitting still. It will be noted that rotation of the seat may be entirely free, or suject to a frictional restraint entirely independent of the just described frictional resistance to horizontal movement.

The upper member 3-A (FIGS. 6-9) of seat support post 3 is telescoped in the outer tube section 40 and contains spring actuator cylinder 50and piston rod 51, which is used to regulate the the effective length of post 3, and hence the height of seat 1. The bottom surface 52 of the rigid bottom part of seat 1 has the straps 53 of a pair of hinge elements 54 secured to it, as by screws 55, so that the seat is pivotally supported on and by hinge pin 56, the middle part of which passes through a bore in a cooperating hinge element 57 formed in a horizontal block 58 which is welded to the post element 3-A. A flange projection 59 of block 58 serves as thrust member for s spring assembly which yieldingly urges the seat up about the axis of binge pin 56 so as to seat the undersurface 52 of the seat on the block 58. The spring assembly comprises a threaded bolt 60, surrounded by a spring 61. Nut 62 below projection 59 limits upward movement (down in FIG. 7, to the right of FIG. 8) of bolt 60, which passes freely through an oversize bore in the projection 59. The head 63 of bolt 60 pushes against thrust plate 64 which is fixed to the seat surface 52, with a force proportional to the tilt of the seat and to the setting of a thrust nut 65. The seat may accordingly be tilted to any desired angle up to a maximum of, say, against the yielding force of the spring. A cam lock lever 66 at one end of the hinge 54-57 may be pulled back to lock the hinge and fix the seat in any desired position of the hinge, and pushing back lever 66 restores the freedom of movement of the parts. Bolt 60 carries a nut or internally threaded collar 67, which may be adjusted along the bolt so as to limit the tilting of the seat, as desired.

As mentioned above, tubular post element 3-A extends down into the tube section 40, being rotatable and slidable therein. A nylon or similar bushing 68 is secured adhesively or otherwise to the lower end of tube 3-A and fits slidably and rotatively in tube 40. A similar bushing 69 is secured in the upper end of tube 40 and fits slidably and rotatively around tube 3-A.

The actuator piston rod 51 has a reduced upper end 70 passing through the central aperture of a thrust annular plate or diaphragm 71 which is welded inside tube 3-A near its upper end. Washer 72, resilient bushing 72' and nut 73, on the threaded end of rod 51, hold the end of the rod in place within tube 3-A, in supporting relation thereto. The actuator clutch or collet operating pin 74 protrudes from the end of rod 51, being spring pressed upwardly so that the cylinder 50 normally locks against movement of its piston rod 51. Cylinder 50 is of a commercially available type, having an inner spring which tends to lift the chair seat 1, so that when pin 74 is depressed, the operator may allow the seat to rise to the desired height or push it down to such height, and releasing pin 74 locks the parts in position. Rod 51 turns freely within cylinder 50, about their common vertical axis. Lever 75, carried on horizontal pin 76 in fork 77 mounted on block 58, permits releasing the actuator lock, by pushing up on the end 77 of the lever so that the other end thereof depresses pin 74.

An annular member 80 welded in the lower end of tubular section 40 accommodates the reduced lower end 81 of the cylinder 50, and is secured thereto by washer 82, snap-ring 83 and resilient bushing 84. The vertical load is thus carried by the actuator, and tubular element 3-A, cooperates with tubular section 40, by means of the bearings 68, 69 to maintain the parts in vertical alignment.

While the stool has been described with reference to a particular type of height adjusting mechanism, other types of spring actuated adjustment may be used, as well as hydraulic adjustments and screw or other mechanical adjustments.

As mentioned above, a foot rail may be provided, and FIGS. 2 and 3 show, by wat of example, foot rail 4 supported directly on the base radii 11 to 15. A rail supported at a distance above these radii may also be used, and provide protection for member 5, where needed. The rail may also be carried by the post element 40 or 3-A) as in the case of some stools now in use.

What is claimed is:

1. A stool comprising a base, seat and seat support post, and an anti-friction hinged arm mechanism sup porting the post over the base with the post axis vertical and permitting free movement horizontally over said base of the post, said hinged arm mechanism comprising a first arm having one end pivotally supported by said base for swinging about a vertical axis and a second arm having one end pivotally carried by the' other end of the first arm for also swinging about a vertical axis, and supporting said post at its other end, and limit means comprising a boundary ring supported by the base and a roller carried by the post in position for engagement with said ring for confining, the movement of the post axis to a predetermined area.

2. A stool according to claim 1, in which the middle of the seat front edge is recessed so as to concentrate support to the buttock and thigh regions of a person seated thereon, the seat surfaces to each side of the so recessed portion being substantially coplanar, and the stool further comprising hinge means supporting said seat for tilting forward about a horizontal axis adjacent the top of the post and parallel to the said seat front edge.

3. A stool according to claim 2 in which the said seat together with its said tilt axis are freely rotatable about the post axis.

4. A stool according to claim 3, in which the post comprises means for adjusting the the length of the post and correspondingly adjusting the height of said seat.

5. A stool according to claim 1, comprising an adjustable friction element for providing a slight frictional resistance to said free movement of said post over said base.

6. A stool according to claim 5, in which said frictional element is carried by the bottom of said post, and comprising a horizontal plate supported by said base and engaged by said frictional element. 

1. A stool comprising a base, seat and seat support post, and an anti-friction hinged arm mechanism supporting the post over the base with the post axis vertical and permitting free movement horizontally over said base of the post, said hinged arm mechanism comprising a first arm having one end pivotally supported by said base for swinging about a vertical axis and a second arm having one end pivotally carried by the other end of the first arm for also swinging about a vertical axis, and supporting said post at its other end, and limit means comprising a boundary ring supported by the base and a roller carried by the post in position for engagement with said ring for confining, the movement of the post axis to a predetermined area.
 2. A stool according to claim 1, in which the middle of the seat front edge is recessed so as to concentrate support to the buttock and thigh regions of a person seated thereon, the seat surfaces to each side of the so recessed portion being substantially coplanar, and the stool further comprising hinge means supporting said seat for tilting forward about a horizontal axis adjacent the top of the post and parallel to the said seat front edge.
 3. A stool according to claim 2 in which the said seat together with its said tilt axis are freely rotatable about the post axis.
 4. A stool according to claim 3, in which the post comprises means for adjusting the the length of the post and correspondingly adjusting the height of said seat.
 5. A stool according to claim 1, comprising an adjustable friction element for providing a slight frictional resistance to said free movement of said post over said base.
 6. A stool according to claim 5, in which said frictional element is carried by the bottom of said post, and comprising a horizontal plate supported by said base and engaged by said frictional element. 